Recently, a hybrid electric vehicle (HEV) has been drawing attention as an eco-friendly vehicle.
In general, the HEV refers to a vehicle that uses two power sources together, which usually correspond to an engine and an electric motor. The HEV not only has excellent fuel efficiency and power performance but also is advantageous in reducing exhaust gas when compared to a vehicle that only includes an internal combustion engine, and thus, has recently been actively developed. Among HEVs, a plug-in hybrid electric vehicle (PHEV) may be connected to a plug to charge a battery that drives an elector motor with external power.
An analog dial-type gauge (hereinafter referred to as an “eco-gauge” for convenience of description), which indicates whether the electric motor is being charged or is driving a wheel and a level thereof, is disposed in a cluster in the HEV. The eco-gauge acquires information about a position to be indicated by a needle from a hybrid controller. Here, the hybrid controller may refer to a controller that controls whether to switch between a driving mode in which only the electric motor is used and a driving mode in which the engine is used together with the motor in the HEV.
A configuration, an operation, and a problem of the eco-gauge will be described with reference to FIGS. 1 and 2.
FIGS. 1A to 1E are diagrams for description of a configuration and a problem of a dial-type gauge of a general HEV.
Referring to FIG. 1A, an eco-gauge 100 of the HEV may broadly include a needle 110 and an area in which the needle 110 moves. The area in which the needle 110 moves includes a charging area 130 indicating charging of a motor on a left side and a driving area 140 indicating driving of the motor on a right side based on a zero point 120. When the ignition is turned OFF (IG OFF), the needle 110 remains at a lowest point 150.
When the ignition is turned ON (READY/IDLE STOP), the needle 110 operates in a rising mode to indicate the zero point 120 as in FIG. 1B.
As driving starts, the needle 110 operates in the rising mode or a dropping mode according to driving conditions as in FIG. 1C.
Incidentally, when the vehicle stops again during driving (that is, enters a READY/IDLE STOP mode), the needle 110 needs to operate in the dropping mode and stop at the zero point 120. However, in practice, the needle 110 may not accurately stop at the zero point 120 due to an error as in FIG. 1D. A picture of an actual eco-gauge experiencing this phenomenon is shown in FIG. 1E.
When the needle 110 returns to the zero point 120 in the dropping mode, the needle 110 may not accurately stop at the zero point 120 due to a scheme in which the needle 110 moves. This phenomenon will be described with reference FIGS. 2A to 2C.
FIGS. 2A to 2C are diagrams for description of a configuration of a stepper motor applied to the dial-type gauge and hysteresis occurring in the stepper motor.
The stepper motor may be applied to an eco-gauge of a general HEV. Here, the stepper motor (or step motor or stepping motor) refers to a motor that moves in steps to rapidly find an accurate position and settle at the position rather than continuously rotating.
FIG. 2A illustrates a configuration of the stepper motor. The stepper motor may include a coil 210, a rotor magnet 220, a rotor gear 230 that rotates by electromagnetic force generated from the coil 210 around the rotor magnet 220, an output gear 250 connected to the needle 110, and an idle gear 240 that delivers a torque between the rotor gear 230 and the output gear 250. This configuration is illustrative, and the idle gear 240 may be omitted or more idle gears may be included according to configuration.
This type of gear structurally has hysteresis, and a tolerance is usually designed in consideration of hysteresis since the gauge vibrates in response to a minute change in input when this tolerance design is not applied.
More specifically, as illustrated in FIG. 2B, a position at which the motor stops when the motor rotates in a positive direction is different from a position at which the motor stops when the motor rotates in a negative direction. Hysteresis of the stepper motor refers to a difference in stopped position at this time.
In general, as illustrated in FIG. 2C, the difference in stopped position corresponds to one step of the stepper motor, that is, one sawtooth 241 of the gear.
Such an error due to hysteresis of the stepper motor occurs at a middle position (that is, zero point) of the gauge. Thus, a problem due to an indication error does not occur in a gauge such as a velocity gauge or a temperature gauge in which a lowest point corresponds to a zero point. However, referring to a gauge such as the eco-gauge in which a zero point is in the middle, a needle cannot accurately indicate the zero point in the middle. Thus, consumers have been filing complaints about indicating the zero point, which is the most sensitive issue. In this way, a problem of quality has been occurring.